The present invention relates to high purity manganese obtained from commercially available electrolytic manganese, and a method for producing the same.
The method of producing commercially available metal manganese is the electrolytic method in which metal manganese is obtained from an ammonium sulfate electrolytic bath, and the commercially available electrolytic manganese obtained with the foregoing method contains roughly several 100 to several 1000 ppm of S and oxygen, which are the cause of non-metal inclusions.
As the method of eliminating S and O from the electrolytic manganese, the sublimation refining method is well known in conventional technologies. Nevertheless, the sublimation refining method has drawbacks of requiring an extremely expensive device, and the production yield being extremely inferior. Moreover, while S and O can be reduced with the sublimation refining method, since there will be contamination from the heater material, capacitor material and other materials of the sublimation refining device, there is a problem in that the metal manganese obtained with the refining method is not suitable as a raw material for electronic devices.
As conventional technologies, Patent Document 1 below describes a method for eliminating sulfur in metal manganese. Specifically, Patent Document 1 describes adding, for example, manganese carbonate which will become a manganese oxide at the melting temperature of a manganese acid compound such as MnO, Mn3O4 and MnO2, and/or metal manganese, melting the metal manganese, to which the manganese compound was added, in an inert atmosphere, and holding the product preferably for 30 to 60 minutes in a molten state so as to attain a sulfur content of 0.002%. Nevertheless, Patent Document 1 fails to specifically describe the existence form and abundance of non-metal inclusions.
Patent Document 2 below describes an electrowinning method of metal manganese, and specifically describes an electrowinning method of metal manganese in which used is an electrolytic solution prepared by adding an oxidizing agent to a solution obtained by excessively dissolving high purity metal manganese in hydrochloric acid and filtering non-dissolved substances, subjecting the obtained solution to neutralization, filtering the produced precipitate, and adding a buffer agent. Patent Document 2 further describes an electrowinning method of metal manganese in which used is an electrolytic solution preferably prepared by further adding metal manganese to the hydrochloric acid solution of metal manganese, adding hydrogen peroxide and ammonia water to a solution obtained by filtering non-dissolved substances, filtering the precipitate produced under mildly acidic or neutral pH, and adding a buffer agent. Patent Document 2, however, fails to specifically describe the existence form and abundance of non-metal inclusions.
Patent Document 3 below describes a method for producing high purity manganese. Specifically, Patent Document 3 describes a method of high purification in which the ion exchange refining method of using chelate resin in the manganese chloride aqueous solution is adopted, and subsequently electrowinning from the refined manganese chloride aqueous solution is performed. Patent Document 3 further describes that, in a dry method, high purity manganese can be obtained from the solid phase manganese via vacuum sublimation refining method (method of selectively condensing and vapor-depositing, at the cooling part, the manganese vapor obtained from the sublimation of the solid phase manganese based on a vapor pressure differential). Patent Document 3, however, fails to specifically describe the existence form and abundance of non-metal inclusions.
Patent Document 4 below describes a method for producing a low oxygen Mn material, and further describes that a Mn material, in which the oxygen content is reduced to 100 ppm or less, can be obtained by subjecting a Mn raw material to induction skull melting in an inert gas atmosphere, and that the acid washing of the Mn raw material prior to the induction skull melting is preferable for seeking the further reduction of oxygen. Nevertheless, Patent Document 4 fails to specifically describe the existence form and abundance of non-metal inclusions.
Patent Document 5 below describes a Mn alloy material for a magnetic material, a Mn alloy sputtering target and a magnetic thin film, and further describes that the oxygen content is 500 ppm or less, S content is 100 ppm or less, and preferably the total content of impurities (elements other than Mn and alloy components) is 1000 ppm or less.
Patent Document 5 further describes that Ca, Mg, La or the like is added as a deoxidizing agent to commercially available electrolytic Mn and high frequency melting is performed in order to eliminate oxygen and sulfur, and that vacuum distillation is further performed after preliminarily melting the electrolytic Mn. Nevertheless, Patent Document 5 fails to specifically describe the existence form and abundance of non-metal inclusions.
Patent Document 6 below describes a method for producing a high purity Mn material and a high purity Mn material for forming a thin film. In the foregoing case, Patent Document 6 describes that coarse Mn is preliminarily melted at 1250 to 1500° C., and, by subsequently performing vacuum distillation at 1100 to 1500° C., a high purity Mn material is obtained. Preferably, the degree of vacuum for the vacuum distillation is set to 5×10−5 to 10 Torr. Patent Document 6 describes that the high purity Mn obtained thereby has a total impurity content of 100 ppm or less, oxygen content of 200 ppm or less, nitrogen content of 50 ppm or less, S content of 50 ppm or less, and C content of 100 ppm or less. Nevertheless, Patent Document 6 fails to specifically describe the existence form and abundance of non-metal inclusions.
Furthermore, Patent Document 7 below describes a sputtering target made from a high purity Mn alloy, Patent Document 8 describes a method for recovering manganese through use of sulfuric acid, and Patent Document 9 describes a method for producing metal manganese by heating and reducing manganese oxide, but none of these Documents specifically describe the existence form and abundance of non-metal inclusions.
Patent Document 1: JP-A-553-8309
Patent Document 2: JP-A-2007-119854
Patent Document 3: JP-A-2002-285373
Patent Document 4: JP-A-2002-167630
Patent Document 5: JP-A-H11-100631
Patent Document 6: JP-A-H11-152528
Patent Document 7: JP-A-2011-068992
Patent Document 8: JP-A-2010-209384
Patent Document 9: JP-A-2011-094207